BK channels are almost ubiquitously expressed and perform many important physiological functions. Dysfunction of the channel causes a variety of diseases, including epilepsy, progressive hearing loss, cerebellar ataxia, and hypertension. The function of BK channels depends on proper subcellular localization and interactions with auxiliary or regulatory proteins. However, the molecular basis of BK channel subcellular localization is unknown and only limited knowledge exists about BK channel auxiliary/regulatory proteins. The powerful molecular genetics of C. elegans is explored to identify proteins important to BK channel function or subcellular localization. In preliminary studies, mutants of three genes (named as bkip-1, bkip-2 and bkip-3) were isolated as suppressors of a lethargic phenotype caused by expressing a gain-of-function (gf) isoform of SLO-1, the C. elegans BK channel. Phenotypes of these mutants included increased neurotransmitter release (bkip-1) and SLO-1 mislocalization (bkip-2 and bkip-3). bkip-1 and bkip-2 were found to encode novel BK channel- interacting proteins whereas bkip-3 remains to be identified. BKIP-1 showed several effects on SLO-1 functional properties when analyzed in a heterologous expression system. This proposal is to test the hypotheses that the three BKIPs are important to SLO-1 function and/or subcellular localization in vivo and that there are other functionally related proteins in C. elegans. The specific aims of this proposal are: (1) determine how BKIP-1 regulates SLO-1 function; (2) determine how BKIP-2 and BKIP-3 control SLO-1 subcellular localization and/or function, and (3) isolate and identify additional mutants that suppress the lethargic phenotype caused by SLO-1(gf), which will be analyzed in future studies. The long-term goal is to elucidate the molecular basis of BK channel function and subcellular localization.